Re: flickering on RealityEngine

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Jim Helman (jimh++at++surreal)
Thu, 27 Jan 94 19:18:01 -0800

> I have a little rendering problem with polygons which are close together
> and far away from the eye point. It seems like Performer cannot decide which
> polygon is visible.

You don't say how far apart the polygons are in depth, but
effective Z buffer resolution drops as range increases. So
while a 1 cm separation may look fine at a few meters, it
won't at a few kilometers, and you'll have Z buffer
"fighting".

If you are rendering nearly co-planar polygons, consider
using a pfLayer to render them. But use them sparingly,
under 1.1 on RealityEngine there is a substantial performance
penalty on pixel fill rates for both the "base" and "decal"
polygons. 1.2 will by default use another mechanism
(displacepolygon) which doesn't have this problem.

But, I'm not sure why it would appear any worse than on
a VGX. Are you sure the near/far clip ranges are the
same. VGX has 24 bit Z. RE has 24 or 32 bit Z, depending
on your msconfig.

rgds,

-jim helman

jimh++at++surreal.asd.sgi.com
415/390-1151
   

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